The project is intended to develop new instrumentation and methods, and to improve existing instrumentation and techniques, for the characterization of biological macromolecules and the study of their interactions. Analytical ultracentrifugation, the techniques ancillary to it, and methods of data analysis using mathematical modeling appropriate for these techniques are the major areas of interest. Studies have continued on the application of mathematical modeling to problems of ultracentrifugal analysis, and on the development of new methods of performing experiments and analyzing data. In particular: (1) Application of the method of implicit constraints to the analysis of simultaneous homogeneous and heterogeneous associations has been achieved. (2) A new method for the analysis of sedimentation velocity experiments has been developed.